EXPERIMENTS IN GEOTECHNICAL ENGINEERING Experiments in Geotechnical Engineering - II: Smt. S. R. PATEL ENGINEERING COLLEGE Dabhi, unjha- 384170 Department of CIVIL engineering Subject : GEOTECHNICAL ENGINEERING-ii Subject code: 160606 Civil Engineering, S. R. Patel Eng. College, Dabhi Page 0
INDEX No. Experiment Page No. Date Sign 1. Auger Boring and Sampling 2. Standard Penetration Test 3. Permeability Test: Constant Head 4. Permeability Test: Falling Head 5. Free Swell and Swell Potential 6. Swelling Pressure Test 7. Model Pile Driving and Pile Load Test Civil Engineering, S. R. Patel Eng. College, Dabhi Page 1
Experiment 1 Date: AUGER BORING AND SAMPLING IS 1892 : 1979 AIM: To collect soil sample using Auger Boring APPARATUS: 1. Hand operated Auger (75 mm dia.) 2. drilling rods 3. guiding plates 4. trowels. PROCEDURE: The hand augers used in boring are about 15 to 20 cm in diameter. These are suitable for advancing holes up to a depth of 3 to 6m in soft soils. The hand auger is attached to the lower end of a pipe of about l8mm diameter. The pipe is provided with a cross-arm at its top. The hole is advanced by turning the cross-arm manually and at the same time applying thrust in the downward direction. When the auger is filled with soil, it is taken out and for the required depth the disturbed samples are preserved in order to determine required physical properties. If the hole is already driven, another type of auger, known as post hole auger is used for taking soil samples. THEORY: An auger is a boring tool similar to one used by a carpenter for boring holes in wood. It consists of shank with a cross-wise handle for turning and having central tapered feed screw. The augers can be operated manually or mechanically. Mechanical augers are driven by power. These are used for making holes in hard strata to a great depth. However, for depths greater than 12m, even mechanical augers become inconvenient and other methods of boring are used. Continuous flight augers are special type of mechanical augers which are provided with a central hollow tube. When the hole is advanced, the central tube is kept plugged. As the auger is turned into the ground, the cuttings rise to the surface through the spiral. During sampling, the plug is removed and a sampler is inserted for taking the samples. The main disadvantage of using a continuous flight auger is that it becomes difficult to ascertain the depth from which the cutting coming on the ground have been removed. Auger boring is generally used in soils which can stay open without casing or drilling mud. Clays, silts and partially saturated sands can stand unsupported. For soils which cannot stand unsupported, especially for sandy soils below water table, a casing is normally required. For such Civil Engineering, S. R. Patel Eng. College, Dabhi Page 2
soils, the method of auger boring becomes slow and expensive. Auger boring cannot be used when there are large cobbles, boulders or other obstructions which prevent drilling of the hole, Auger borings are particularly useful for subsurface investigations of highways, railways and air fields, where the depth of exploration is small. The investigations are done quite rapidly and economically by auger boring. The main disadvantage of the auger boring is that the soil samples are highly disturbed. Further, it becomes difficult to locate the changes in the soil strata. BORE LOG Date of Boring: Location of Boring : Boring No.: Type of Boring: Water Table: Type of Sampler: Soil Description Soil Indentification Depth of Strata Sample Type Ѡ (%) Ѡ L (%) Ѡ P (%) Ѡ S (%) G Cu Kg/ cm 2 Ǿ Civil Engineering, S. R. Patel Eng. College, Dabhi Page 3
Water Content Determination by oven drying method for depth, in m = Sr. No. Description Sample-l Sample-2 1 Container No. 2 Mass of container and wet soil W2, in g 3 Mass of container and dry soil W3, in g 4 Mass of container WI, in g 5 Mass of dry soil (W3- WI), in g 6 Mass of moisture (W2- W3), in g 7 Water content co = W2 W3 W3 Wl 8 Average water content, in % xl00, In % Liquid Limit Determination by cone penetration method for depth, in m = Civil Engineering, S. R. Patel Eng. College, Dabhi Page 4
Specific Gravity of soil for depth in m= Room trmperature t 0 C= 1 Weight of density bottle 2 Weight of density bottle + dry soil 3 Weight of density bottle + dry soil + water 4 Weight of density bottle + water 5 Specific gravity of soil G= (W2- W1) (W4 W1) (W3 W2) W1 g W2 g W3 g W4 g G 1 2 3 Average sp. Gravity of soil at T t Average sp. Gravity of soil at 27 O c Particle size distribution sheet for depth in m= Mass of dry soil sample in g= Sr. no. IS Sieve 1 4.75 mm Particle (mm) size Mass retained (g) % Retained Cumulative % retained Cumulative % finer (N) 2 2.36 mm 3 1.18 mm 4 600µ 5 425µ 6 300µ 7 150µ 8 75µ Civil Engineering, S. R. Patel Eng. College, Dabhi Page 5
Determination of Shear Parameters for the depth, in m: Cross-sectional area of the specimen, cm2: Bulk Density of soil: Sr.No. Normal Stress,Kg/cm2 Proving Ring Reading (div) Shear Force,kg Shear Stress,kg/cm2 cu, kg/cm2 Ø Conclusion: Sign Civil Engineering, S. R. Patel Eng. College, Dabhi Page 6
Experiment 2 Date: IS :2131-1981 STANDARD PENETRATION TEST AIM: To determine the resistance of soil against penetration APPARATUS: 1. Tripod 2. manila rope 3. doughnut hammer of weight 63.5kg 4. anvil 5. split spoon sampler 6. driving rod. PROCEDURE: The standard penetration test is conducted in a bore hole using a standard split- spoon sampler. when the bore hole has been drilled to the desired depth, the drilling tools are removed and the sample is driven into the soil by a drop hammer of 63.5kg mass falling through a height of 750mm at the rate of30 blows per minute (IS: 2131-1963).the number of hammer blows required to drive 150mm of sample is counted. The sample is further driven by 150 mm and the number of blows recorded. Likewise, the sampler is once again further driven by 150 mm and number of blows recorded. The number of blows recorded for the first 150 mm is disregarded. The number of blows recorded for the last two 150 mm intervals are added to give standard penetration number (N).in other words, the standard penetration number is equal to the number of blows required for 300 mm penetration beyond a seating drive of 150 mm. If the number of blows for 150 mm drive exceeds 50, It is taken as refusal and test is discontinued. If the split spoon sampler is driven less than 45cm (total), then the penetration will be for the last 30cm of penetration (if less than 30cm is penetrated, the logs should state the number of blows and the depth of penetration. THEORY: The standard penetration test is most commonly used in in-situ test, especially for cohesion-less soils which cannot be easily sampled. The test is extremely useful for determining the relative density and the angle of shearing resistance of cohesion-less soils. It can also be used to determine the unconfined compressive strength of cohesive soils. The standard penetration number is corrected for dilatancy correction and overburden correction and overburden correction as explained below. Civil Engineering, S. R. Patel Eng. College, Dabhi Page 7
(a) Dilatancy correction: Silty fine sand and fine sand below the water table develop pore pressure which is not easily dissipated. The pore pressure increases the resistance of the soil and hence the penetration number (N).Terzaghi and peak (1967) recommend the following correction in the case of silty fine sands when the observed value of N exceeds The corrected penetration number, Ne = 15 + 1 2 (NR-15) Where N R is recorded value and N C is the corrected value N R 15, N C = N R (b) Overburden pressure correction: In granular soils, the over burden pressure affects the penetration resistance. If the two soils having same relative density but different confining pressures are tested, the one with higher confining pressure gives a higher penetration number. As the confining pressure in cohesion-less soils increases with the depth, the penetration number for soils at shallow depths is underestimated and that at greater depth is overestimated. For uniformity, the N-values obtained from field test under different effective overburden pressures are corrected to a standard effective overburden pressure. Gibbs and Holtz (1957) recommend the use of the following equation for dry or moist clean sand. Ne = NR X 350 σ+70 Where N R observed N value and σ = effective overbidding pressure. The eq2.2 is only applicable for cr :::; 280 kn/m2. The ratio ( Ne / NR ) should lie between 0.45 and 2.0.if ( Ne / NR ) ratio is greater than 2.0, Ne should be divided by 2.0 to obtain the design value used in finding the bearing capacity of the soil. The correction may be extended to saturated silty sand and fine sand after modifying the NR according to Eq.2.2, i.e. Nc obtained from Eq. 2.2 would be taken as NR In Eq. 2.1. Thus the overburden correction is applied first and then the dilatancy correction is applied. Peck, Hansen and Thornburn (1974) give the chart for correction of N- values to an effective overburden pressure of96 kn/m2, according to them. Correction is given by Bazaara (1967), and also by Peck and Bazaara (1969), is one of the commonly used corrections. According to them, Civil Engineering, S. R. Patel Eng. College, Dabhi Page 8
Where N = N R, if σ = 71.8 Kn/m 2 The value of the standard penetration number N depends upon the relative density of the cohession-less soil and the unconfined compressive strength of cohesive soil. If the soil is compact or stiff, the penetration number is high. The angle of shearing resistance ((j)) of the cohesion-less soil depends upon the number N. in general, greater the N-value, the greater shearing resistance table 2.1 gives the average values of a for different ranges of N The consistency and the unconfined shear strength of the cohesive soils can be approximately determine from the SPT number N. as the correlation is not dependable, it is advisable to determine the shear strength of the cohesive soils by conducting shear test on undisturbed samples or by conducting in-situ vane shear test. Table 2.2 gives the approximate value of the unconfined shear strength for different ranges of N the unconfined compressive strength can also be determined from the following relation. N Denseness (jj 0-4 Very loose 25 u _32 u 4-10 Loose 27 u -35 u 10-30 Medi um 30 u _40 u 30-50 Dense 35 u _45 u >50 Very Dense >45 u N Denseness {jl/ (kn/ji/) 0-2 Very soft <25 2-4 Soft 25-50 4-8 Medium 50-100 8-15 Stiff 100-200 15-30 Very stiff 200-400 Hard >400 A sub-soil investigation report should contain the data obtained from bore holes, site observations and laboratory results. It should also give recommendations about the suitable type of foundation, allowable soil pressure and expected settlements. It is essential to give a complete and accurate data collected. Each bore hole should be identified by code number. The Civil Engineering, S. R. Patel Eng. College, Dabhi Page 9
location of each bore hole should be fixed by measurement of its distance or angles from some permanent feature. All relevant data for the bore is recorded in a boring log. A boring hole gives description or classification of various strata encountered at different depth. Any additional information that is obtained in the field, such as soil consistency, unconfined compressive strength, standard penetration test, cone penetration test, is also indicated on boring log. It should also show water table. If the laboratory tests have been conducted, the informaton abollt index properties, compressibility, shear strength, permeability, etc should also be provided. The data obtained from a series of bore holes is presented in the form of a sub-surface profile. Sub-surface profile is a section tlu'ough the ground along the line of exploration. It indicates the boundaries of different strata, along with their classification. It is important to remember that conditions between bore holes are estimated by interpolation, which may not be correct. Obviously, the larger the number of holes, the more accurate is the sub-surface profile. The site investigation report should contain the discussion of the results. The discussion should be clear and concise. The recommendations about the type and depth of foundation, allowable soil pressure and expected settlements should be specific. The main findings of the report are given in conclusion. (1) Introduction, which gives the scope of investigation. (2) Description of proposed structure, the location and geological conditions at the site. (3) Details of the field exploration programme, indicating the number of borings,tbeir location and depth. (4) Details of the methods of explorations. (5) General description of the sub-soil conditions as obtained from in-situ tests, such as standard penetration test, cone penetration test. (6) Details of the laboratory test conducted on the soil samples obtained and the results obtained. (7) Depth of ground water table and changes in water levels. (8) Discussion of the results. (9) Recommendations about the allowable bearing pressure, the type of foundation or (10) Conclusion the main findings of the investigations should be clearly stated. it should be brief but should mention salient points. (11) Limitations of the investigations should also briefly stated. Civil Engineering, S. R. Patel Eng. College, Dabhi Page 10
Civil Engineering, S. R. Patel Eng. College, Dabhi Page 11
BORE LOG Date of Boring: Location of Boring : Boring No.: Water Table: Type of Boring: Type of Sampler: Soil Descriptio n Soil Indentification Depth of Strata Sample Type Ѡ (%) Ѡ L (%) Ѡ P (%) Ѡ S (%) G Cu Kg/ cm 2 Ǿ I) Type of foundation: 2) Depth of foundation: 3) Width of foundation: 4) Allowable settlement: 5) Factor of safety: Civil Engineering, S. R. Patel Eng. College, Dabhi Page 12
TERZAGHI'S BEARING CAPAITY FACTORE Ø General shear failure Local shear failure Nc Ns Nr Nc' Ns' Nr' 0 5.7 1.0 0.0 5.7 1.0 0.0 5 7.3 1.6 0.5 6.7 1.4 0.2 10 9.6 2.7 1.2 8.0 1.9 0.5 15 12.9 4.4 2.5 9.7 2.7 0.9 20 13.3 7.4 5.0 11.8 3.9 1.7 25 25.1 12.7 9.7 14.8 5.6 3.2 30 37.2 22.5 19.7 19.0 8.3 5.7 34 52.6 36.5 35.0 23.7 11.7 9.0 35 52.8 41.5 42.4 25.2 12.6 10.1 40 95.7 81.3 100.4 34.9 20.5 18.8 45 172.3 123.3 297.5 51.2 35.1 37.7 48 258.3 287.9 730.1 66.8 50.5 60.4 50 347.5 415.1 1153.2 81.3 65.6 87.1 BEARING CAPACITY FACTORES (IS: 6403-1981) Ø Nc Ns Nr Ø Nc Ns Nr 0 5.14 1.00 0.00 1 5.38 1.09 0.07 26.00 22.25 11.85 12.54 2 5.63 1.20 0.15 27.00 23.94 13.20 14.47 3 5.90 1.31 0.24 28.00 25.80 14.72 16.72 4 6.19 1.43 0.34 29.00 27.85 10.44 19.34 5 6.49 1.57 0.45 30.00 30.14 18.40 22.40 6 6.81 1.72 0.57 31.00 32.67 20.63 25.99 7 7.16 1.88 0.71 32.00 35.49 23.18 30.22 8 7.53 2.06 0.86 33.00 38.64 26.09 35.19 9 7.92 2.25 1.03 34.00 42.16 29.44 41.06 10 8.35 2.47 1.22 35.00 46.12 33.30 48.03 11 8.80 2.71 1.44 36.00 50.59 37.75 56.31 12 9.28 2.97 1.69 37.00 55.63 42.92 66.19 13 9.81 3.26 1.97 38.00 61.35 48.93 78.03 14 10.37 3.59 2.29 39.00 67.37 55.96 92.25 15 10.98 3.94 2.65 40.00 75.31 64.20 109.41 16 11.63 4.34 3.06 41.00 83.86 73.90 130.22 17 12.34 4.77 3.53 42.00 93.71 85.38 155.55 18 13.10 5.26 4.07 43.00 105.11 99.02 186.54 19 13.93 5.80 4.68 44.00 118.37 115.31 224.64 20 14.83 6.40 5.39 45.00 133.88 134.88 271.76 21 15.82 7.07 6.20 46.00 152.10 158.51 330.35 22 16.88 7.82 7.13 47.00 173.64 187.21 403.67 23 18.05 8.66 8.20 48.00 199.26 222.31 496.01 24 19.32 9.60 9.44 49.00 229.93 265.51 613.16 25 20.72 10.66 10.88 50.00 266.89 319.07 762.89 Civil Engineering, S. R. Patel Eng. College, Dabhi Page 13
Civil Engineering, S. R. Patel Eng. College, Dabhi Page 14
Civil Engineering, S. R. Patel Eng. College, Dabhi Page 15
Sr. Description Sample-I Sample-II Sample-III Sample-IV No; 1 Depth, m 2 Observed SPT No., N R 3 Corrected SPT No., Nc 4 Field Density, gm/cc 5 Field Water Content, % 6 Liquid Limit, % 7 Plastic Limit, % 8 C, kg/cm 2 9 <1> 10 Average N value 11 Design <1> value 12 Design C value SBC by shear criteria, kn/m 2 : 13 N-<1> Correlation 14 Peck Method 15 I.S. code method SBC by settlement criteria, kn/m 2 : 16 Terzaghi and Peck 17 Teng's Equation Conclusion: Sign Civil Engineering, S. R. Patel Eng. College, Dabhi Page 16
Experiment 3 Date: PERMEABILITY TEST: CONSTANT.HEAD IS 1892 : 1979 AIM : To determine the coefficient of permeability test using Jodhpur Permeameter. of soil in the laboratory by constant head APPARATUS : 1. Jodhpur permeameter 2. de-aired water 3. 4.75mm and 2mm IS sieves 4. mixing pan 5. stop watch 6. graduated measuring cylinder 7. beaker, and thermometer. PROCEDURE: A. Preparation of dynamically compacted remoulded soil specimen: I) Take 800 to 1000g of representative specimen of soil and raise its water content to the optimum water content. Leave the soil mix in an sir tight container for some time. 2) Assemble the permeameter for dynamic compaction. For this, grease the mould lightly from inside and place it upside down on the dynamic compaction base. Find the mass of the assembly accurate to Ig. Put the 3cm collar to the other end. 3) Compact the wet soil mix in two layers, with 15 blows of the 2.5kg dynamic ramming tool, given to each layer. Remove the collar and trim off the excess soil. Find the mass of mould assembly with soil. The difference of the two masses taken in step 2 & 3 would give mass M of the compacted soil. 4) Place filter paper or fine wire mesh on the top of soil specimen and fix the perforated base plate on to it. 5) Turn the assembly upside down and remove the compaction plate. Place the top perforated plate on the top of the soil specimen and fix the top cap on to it, after inserting the sealing gasket. 6) Now saturate the sample to about 70cm of mercury. METHOD: l) Place the mould assembly in the bottom tank and fill the bottom tank with water up to its outlet. Civil Engineering, S. R. Patel Eng. College, Dabhi Page 17
2) Connect the outlet tube of the constant head tank to the inlet nozzle of the permeameter, after removing the air in the flexible rubber tubing connecting the tube. Adjust the hydraulic head either by adjusting the relative heights of the permeameter mould and the constant head tank, or by raising or lowering the air intake tube with in the head tank. 3) Start the stop watch and at the same time put a beaker under the outlet of the bottom tank. Run the test for some convenient time interval. Measure the quantity of water collected in the beaker during the test. 4) Repeat the test twice more, under the same head and for same interval of time. Observation Table: Sr. No. Description 1 Area of stand pipe a, in cn/ 2 Length of specimen L, in em 3 CIs area of the soil specimen A, em.! 4 Initial head hi> in em Final head h 2, in em 5 6 Time interval t, in see (a) I test (b) II test (c) III test Average 7 Coefficient of permeability at test temperature, in em/see 8 Test temperature, DC 9 Permeability at 27 DC, in em/see Calculation: K= Q L T t h a Conclusion: Sign Civil Engineering, S. R. Patel Eng. College, Dabhi Page 18
Experiment 4 Date: PERMEABILITY TEST: FALLING HEAD AIM: To determine the coefficient of permeability of soil in the laboratory by falling head test using Jodhpur Permeameter. APPARATUS: 1. Jodhpur permeameter 2. de-aired water 3. 4.7Smm and 2mm IS Sieves 4. mixing pan 5. stop watch 6. graduated measuring cylinder 7. beaker 8. thermometer. PROCEDURE: 1. Prepare the remoulded soil specimen in the permeameter and saturate it. 2. Keep the permeameter mould assembly in the bottom tank and fill the bottom tank with water upon its outlet. 3. Connect the eater inlet nozzle of the mould to the stand pipe filled with water. Permit water to flow for some time till steady state of flow is reached. 4. With the help of the stop watch, note the time interval required for the water level in the stand pipe to fall from some convenient initial value to some final value. 5. Repeat the step at least twice and determine the time for the water level in the stand pipe to drop from the same initial head to the same final value. 6. In order to determine the inside area of the cis of the stand pipe, collect the quantity of water contained in between two graduations of known distance apart. Find the mass of this water accurate to O.1g. The mass in gms divided by the distance, I em, between the two graduations will give the inside area of cross-section of the stand pipe. Civil Engineering, S. R. Patel Eng. College, Dabhi Page 19
Observation Table: Sr. No. Description 1 Area of stand pipe a, in cn/ 2 Length of specimen L, in em 3 CIs area of the soil specimen A, em.! 4 Initial head hi> in em Final head h 2, in em 5 6 Time interval t, in see (a) I test (b) II test (c) III test Average 7 Coefficient of permeability at test temperature, in em/see 8 Test temperature, DC 9 Permeability at 27 DC, in em/see Calculation: K=2.3 a L A t log 10 h1 h2 Conclusion: Sign Civil Engineering, S. R. Patel Eng. College, Dabhi Page 20
Experiment 5 Date: PROCEDURE: FREE SWELL AND SWELL POTENTIAL Take two 109 soil specimen of oven dry soil passing through 425 11 I.S. sieve. Each specimen of soil shall be poured in each of the two glass graduated cylinders of 100mi capacity. One cylinder shall then be filled with kerosene oil and the other with distilled water up to the 100mi mark. After the removal of entrapped air (by gentle shaking or stirring with a glass rod), the soil in both the cylinders shall be allowed to settle. Sufficient time (not less than 24hrs) shall be allowed for the soil sample to attain equilibrium state of volume without any further change in the volume of the soils. The final volume of the soils in each of the cylinders shall be read out. Note: The case of highly swelling soils, such as sodium bentonites, the sample size may he 5 g or alternatively a cylinder of250 ml capacity may be used. Theory: Free swell is the increase in volume of a soil, without any external constraints, on submergence in water. The possibility of damage to structures due to swelling of expansive clays need be identified, at the outset, by an investigation of those soils likely to possess undesirable expansion characteristics. Inferential testing is resorted 'to reflect the potential of the system to swell under different simulated conditions. Actual magnitude of swelling pressures developed depends upon the dry density, initial water content, surcharge loading and several other environmental factors. The level of the soil in the kerosene graduated cylinder shall be read as the original volume of the soil samples, kerosene being a non-polar liquid does not cause swelling of the soil. The level of the soil in the distilled water cylinder shall be read as the free swell level. The free swell index of the soil shall be calculated as follows: Free swell index, percentage= Vd Vk, Vk Where Vd =the volume of soil specimen read from the graduated cylinder containing distilled water, Vk = the volume of soil specimen read from the graduated cylinder containing kerosene. Conclusion: Sign Civil Engineering, S. R. Patel Eng. College, Dabhi Page 21
Experiment 6 Date: SWELLING PRESSURE TEST AIM: to determint the sewlling pressure of soil. APPARATUS: 1. Consolidometer (specimen diameter = 60mm, height of specimen = 20mm, the ratio of diameter of the particles to the thickness of the specimen should be minimum 3) 2. brass rings, porous stones (minimum thickness = l5mm) 3. dial gauges (LC= 0.01 mm & range 20mm) 4. water reservoir 5. moisture room 6. soil trimming tools 7. oven 8. desiccator 9. balance (sensitive to 0.01 gm) 10. containers. PROCEDURE: The consolidation specimen ring with the specimen shall be kept between two porous stones saturated in boiling water providing a filter paper (Whatman No. 1 or equivalent) between the soil specimen and the porous stone. The loading block shall then be positioned centrally on the top of the porous stone. This assembly shall then be placed on the platen of the loading unit as shown in figure. The load measuring proving ring tip attached to the load frame shall be placed in contact with the consolidation cell without any eccentricity. A direct strain measuring dial gauge shall be fitted to the cell. The specimen shall be inundated with distilled water and allowed to swell. The initial reading of the proving ring shall be noted. The swelling of the specimen with increasing volume shall be obtained in the strain measuring load gauge. To keep the specimen at constant volume, the platen shall be so adjusted that the dial gauge always shows the original reading. This adjustment shall be done at every 0.1 mm of swell or earlier. The dial gauge readings shall be taken till equilibrium is reached. This is ensured by making a plot of swelling dial reading versus time in hours, which plot becomes asymptotic with abscissa (time scale). The equilibrium swelling is normally reached over a period of 6 to 7 days in general for all expansive soils. The assembly shall then be dismantled and the soil specimen extracted from the consolidation ring to determine final moisture content. Civil Engineering, S. R. Patel Eng. College, Dabhi Page 22
Calculation: The difference between the final and initial dial readings of the proving ring gives total load in terms of division which when multiplied by the calibration factor gives the total load. This when divided by the cross-sectional area of the soil specimen gives the swell pressure expressed in kn/m2 ( kgf/cm2 ). OBSERVATION: 1. Undisturbed/Remoulded soil: 2. Liquid limit of soil: 3. Plasticity Index of soil: 4. Specific Gravity of soil: 5. Bulk/natural density of soil: 6. Field moisture content of soil: SWELL PRESSURE DATA Date Time Strain dial Rdg before Adjustment Proving ring Reading Difference Load in Kg Swell Pressure in Kg/cm 2 Remark Swelling Pressure in(kg/cm 2 ) = of proving ring Final dial reading Initial dial reading Area of specimen X Calibration Factor Conclusion: Sign Civil Engineering, S. R. Patel Eng. College, Dabhi Page 23
Experiment 7 Date: MODEL PILE DRIVING AND PILE LOAD TEST APPARATUS: 1. Model tank 2. model test pile 3. air dry sand 4. dial gauges 5. hydraulic jack. PROCEDURE: A. Reaction: The reaction may be obtained by kentledge placed on a platform supported clear of the test pile. In centre of gravity of the kentledge should generally be on the axis of the pile and the load applied by the jack should also be coaxial with this pile. The reaction to be made available for the test should be 25% more than the final test load proposed to be applied. B. Safe Load: The safe load on single pile for the initial test should be least of the following: 1. Two-thirds of the final load at which the total displacement attains a value of l2mm unless otherwise required in a given case on the basis of nature and type of the structure in which case, the safe load should be corresponding to the stated total displacement permissible. 2. 50% of the final load at which the total displacement equal 10% of the pile diameter in case of uniform diameter piles and 7.5% of the bulb diameter in case of under-reamed piles. C. ERP Test method: This method is used for determining ultimate bearing capacity of pile. This method is not useful to predict settlement of the pile under working load conditions. The load shall be measured by means of pressure of 0.01 mm sensitivity load gauge. The penetration (deflection) should be measured by means of dial gauges held by a datum bar resting on immovable supports at a distance of at least 3D (subject to minimum of 1.5m) away from the test pile edge. D. is pile stem diameter of circular piles or diameter of the circumscribing circle in the case of square or non-circular piles. One of the dial gauges will be selected for conducting the test. With continuous application of pressure on the pile top by the operating jack, a person watches the rate settlement of the dial gauge against a stop watch held in his hand and directs the pump operator to pump faster or slower or at the same rate as needed to maintain the prescribed rate of settlement say at every 0.25mm settlement, he gives an indication to take readings. Immediately, other persons record the pressure gauge readings and other dial gauge readings. Civil Engineering, S. R. Patel Eng. College, Dabhi Page 24
The pump supplying the jack may be hand or mechanically operated. For force up to 200ton hand pumping is convenient. The jack should be operated to cause the pile to penetrate at uniform rate which may be controlled by checking the time taken for small increments of penetration and adjusting the pumping rate accordingly. Reading of time, penetration and load should be taken at sufficiently close intervals to give adequate control of the rate of penetration. A rate of penetration of about 0.75mm per min is suitable for predominantly friction piles. For predominantly end-bearing piles in sand or gravel, rate of penetration of 1.5mm per minute may be used. The rate of penetration, if steady, may be half or twice these values without significantly affecting the results. The test should be carried out for the penetration more than 10% of the diameter of the pile base. OBSERVATION: Type of pile: Depth of model pile: Cross-sectional area of pile: Type of soil: Pile material: Capacity of jack: Sr. No. Time, in sec Depth of penetration, in mm Load, in Kn Conclusion: Civil Engineering, S. R. Patel Eng. College, Dabhi Page 25 Sign